The present invention relates to catheters that can be placed in bodily conduits. The invention particularly relates to dilatation balloons and catheters using such balloons for administering treatments to widen constricted passages in, for example, angioplasty, valvuloplasty, or urological procedures.
One example of such a procedure, angioplasty, is used to treat a stenosis, i.e. to restore adequate blood flow to a region of a blood vessel which has been narrowed to such a degree that blood flow is restricted. Frequently the stenosis can be expanded so that the vessel will permit an acceptable blood flow rate. Coronary angioplasty, for example, includes the insertion of a balloon catheter through a patient's coronary artery to an arterial stenosis and injecting a suitable fluid into the balloon to inflate it, hence expanding the stenosis radially outwardly. Angioplasty has proven to be a successful alternative to coronary arterial bypass surgery.
Typically, balloon catheters have a balloon fastened at at least one end around the exterior of a hollow catheter shaft. The hollow interior of the balloon is in fluid flow relation with the hollow interior of the shaft. The shaft then may be used to provide a fluid supply for inflating the balloon.
Presently used catheter balloons may be classified as compliant or non-compliant balloons. Compliant balloons expand and stretch with increasing pressure within the balloon, and are made from such materials as polyethylene or polyolefin copolymers. Non-compliant balloons, made from such materials as polyethylene terephthalate (PET) or polyamides, remain at a preselected diameter as the internal balloon pressure increases beyond that required to fully inflate the balloon.
Compliant balloon materials provide a degree of softness to the balloon which aids its passage through, e.g., blood vessels with minimal trauma. Known compliant balloon materials also can display good abrasion and puncture resistance at thicknesses typically used for medical device balloons. However, as mentioned above, they do not remain at the desired diameter with increasing pressure. Such compliant balloons also lack sufficient hoop strength to achieve high dilating forces.
A non-compliant balloon, that is one remaining at a preselected diameter regardless of increasing pressure, is often desirable. Typical non-compliant balloon materials do not exhibit the same degrees of softness and abrasion resistance as the compliant balloons.
It would be desirable, for many treatment conditions, to have a dilatation balloon exhibiting the combined characteristics of softness, abrasion and puncture resistance, hoop strength, and the ability to maintain a preselected diameter as the internal pressure within the balloon is increased. The balloon described herein was developed to address that need.